Explanation:
The complex shell of a star seen to explode
300 years ago is helping astronomers to
understand how that star exploded.
This
Chandra Observatory image of supernova remnant
Cassiopeia A (Cas A) shows unprecedented detail in three
x-ray colors.
The relationship between brightness, color,
and position of material in the image indicates
where in the star this material was just before
the explosion.
Bright knots on the left, for example, contain little iron,
and so are hypothesized to originate from a higher layer
than outer red filaments, which are iron rich.
The blue region on the right is seen through absorbing
dust,
and so appears depleted of low-energy x-rays.
It takes light ten years to cross the gas shell of the
Cas A supernova remnant, which is 10,000
light-years distant.
Most of the
elements
that make people and planets were produced in
supernova explosions.